Amino Acid Metabolism Flashcards
The basic structural units of proteins are
amino acids
There are …. common amino acids found in proteins
20
What is an α carbon?
it is a tetrahedral carbon at the centre of an amino acid
Describe the basic amino acid structure
- α-Carbon is chiral (except in glycine)
- at pH of 7.0, uncharged amino acids are zwitterions
- they have a tetrahedral structure
- α-carbon is bonded to an amino group(NH2) and a carboxyl group(COOH) on the other side
- a 3rd bond is always to H and the 4th bond is to a variable side chain(R)
6 properties of amino acids
- capacity to polymerize
- novel acid-base properties
- varies structure and chemical functionality
- chirality
- differ from each other by the R group
- R group influences solubility in water
The 5 main classes of the common amino acids based on the reactivities of their R groups
- Aliphatic non-polar
- Aromatic
- Polar uncharged
- Polar negatively charged
- Polar positively charged
Name all the aliphatic non-polar amino acids
Clue: GAVLIPM
Glycine Alanine Valine Leucine Isoleucine Proline Methionine
Name the aromatic amino acids
Clue: PTT
- Phenylalanine
- Tryptophan
- Tyrosine
Name the polar uncharged amino acids
Clue: STCAG
- Serine
- Threonine
- Cysteine
- Asparagine
- Glutamine
Name the polar negatively charged amino acids
Clue: AG
- Aspartate
2. Glutamate
Name the polar positively charged amino acids
Clue: LAH
- Lysine
- Arginine
- Histidine
How are amino acids classified based on nutritional requirement?
Essential
Non-essential
Semi-essential
Name the essential amino acids
Clue: HILL MPT TV
Histidine Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine
Name the non-essential amino acids
Clue: 4A C 3G PST
Alanine Arginine Asparagine Aspartate Cysteine Glycine Glutamine Glutamate Proline Serine Tyrosine
Name the semi-essential amino acids
Clue: ACGGPT
Arginine Cysteine Glutamine Glycine Proline Tyrosine
When is Methionine produced in large amounts?
When cysteine is not adequately supplied in the diet, to produce cysteine
When is Phenylalanine produced in large amounts?
when tyrosine is adequately supplied in the diet, it is needed to form tyrosine
How are amino acids groups based on catabolic intermediates?
Glucogenic and Ketogenic
What are glucogenic amino acids catabolized to?
pyruvate α-ketoglutarate fumarate succinyl CoA oxaloacetate
Examples of glucogenic amino acids
Clue: 4A C GH MPTV
Alanine Arginine Asparagine Aspartate Glutamine Histidine Methionine Proline Threonine Valine
What are ketogenic amino acids catalyzed to?
acetyl CoA and acetoacetyl CoA
Purely ketogenic amino acids
Clue: 2L
Leucine
Lysine
Both glucogenic and ketogenic amino acids
Clue: IPTT
Isoleucine
Phenylalanine
Tryptophan
Tyrosine
What are unusual amino acids?
they are formed from the modification of common amino acids
3 examples of unusual amino acids
hydroxyproline
ornithine
norleucine
What are the 4 general reactions of amino acids?
- Decarboxylation
- Transamination
- Oxidative deamination
- Transdeamination
Amino acids are decarboxylated to form ……….
amines.
eg. 1. Histamine from Histidine
2. L-Dopa from Tyrosine
3. Serotonin from Tryptophan
What is transamination?
transfer of amino group from an amino acid to an α-keto-acid to from the corresponding amino acid
What enzyme catalyzes transamination and what prosthetic group does it require?
amino transferases
requires pyridoxal phosphate (PLP), a derivative of vitamin B6
What’s the function of PLP?
it is an intermediate carrier of the amino groups at the active site of amino transferase
What type of transformation does PLP undergo?
reversible transformation between the aldehyde form and the aminated form, pyridoxamine phosphate
In mammals, which amino acids can’t be transaminated?
Lysine
Threonine
What type of reaction can’t proline participate in and why?
PLP dependent reactions including transamination and decarboxylation
because it has a secondary amino group
Where does oxidative deamination of glutamate occur?
mitochondria of the liver cells
What are the products of oxidative deamination of glutamate and which enzyme catalyzes the reaction?
α-ketoglutarate and ammonium ions
glutamate dehydrogenase is the enzyme
When does glutamate dehydrogenase activity increase?
when hepatocytes require fuel from TCA
What are the allosteric activators and inhibitors of glutamate dehydrogenase?
AA- GDP& ADP
AI- GTP&ATP
What is transdeamination?
the combined action of amino transferases and glutamate dehydrogenase
What does the coupling of oxidative deamination and transamination do?
creates an avenue for deaminating all amino acids
